Spectroscopic method and apparatus for measuring optical radiation

Abstract

The intensity 2 of radiation coming from an object 1 to be measured and illuminated by collimated radiation is measured at several wavelengths by focusing the radiation, via a lens 4 and a planar mirror 6, on a detector group 3 having several detector elements (3a to 3d). The radiation coming from the object is directed by the lens and the mirror such that, by rotating the mirror, tilted at a small angle with respect to its axis 5, around this axis and by keeping the radiation on the surface of the mirror, the focus F of radiation is moved in a detector plane D along an uninterrupted circular path R crossing each detector element positioned substantially in the same plane and excited at a different wavelength.

We claim: 
     
       1. A method of spectroscopically measuring optical radiation, in which the intensity of radiation coming from an object (1) to be measured and exposed to collimated radiation is measured at a plurality of different wavelengths by focusing the radiation, via optical means (4) and mirror means (6), on a detector group (3) comprising a plurality of detector elements (3a to 3d), comprising the steps of: a) orienting the optical means to direct the radiation to a planar surface of the mirror means, said planar surface being tilted at a small acute angle (α) relative to a plane perpendicular to a rotational axis (5) of the mirror means,   b) rotating the mirror means around said axis such that a focus (F) of the radiation moves in and defines a continuous, repetitious path (R) in a detection plane, and   c) disposing the detector group with detection surfaces of the detector elements lying in said detection plane and in said path, such that the moving radiation focus repeatedly sweeps across the detection surfaces of the elements.   
     
     
       2. A method according to claim 1, wherein said path (R) is substantially circular or ellipsoidal. 
     
     
       3. A method according to claim 1, wherein the focus (F) is broadened in the detector plane (D) by integral diffuser means (9) on the mirror means (6). 
     
     
       4. A method according to claim 1, wherein the optical means comprises a focusing lens. 
     
     
       5. A device for spectroscopically measuring optical radiation, comprising: a) means (200, 210) for lighting an object 1,7) to be measured with substantially parallel radiation,   b) optical focusing means (4) for directing radiation (2) coming from the object to be measured, and   c) planar mirror means (6) rotatable around an axis thereof for deflecting the radiation to a detector group (3) comprising a plurality of detector elements (3a to 3d), wherein   d) the focusing means (4) is disposed between the object and the mirror means (6) such that the radiation coming from the optical focusing means is reflected by the planar surface of the mirror means and focused in a detection plane (D),   e) the planar surface of the mirror means is tilted at a small acute angle (α) with respect to a plane perpendicular to an axis (5) thereof, and   f) the mirror means (6) is rotatable around said axis such that detection surfaces of the detector elements (3a to 3d) situated in the detection plane are repeatedly and sequentially swept by the focus (F) of the radiation moving in a continuous, repetitious path (R).   
     
     
       6. A device according to claim 5, wherein the mirror means (6) comprises a substantially integral aluminium member. 
     
     
       7. A device according to claim 5, further comprising diffuser means defined by roughness (9) formed on the surface of the mirror means. 
     
     
       8. A device according to claim 5, wherein the tilt angle (α) of the mirror means surface is less than 10°, preferably approximately 6°. 
     
     
       9. A device according to claim 5, wherein said path (R) is substantially circular or ellipsoidal. 
     
     
       10. A device according to claim 5, wherein said detection surfaces of the detector elements are defined by ends (24a-24n) of fiber optic members.